San Bernardino County’s housing market saw a 12 percent drop in sales in December when compared to a year ago, according to a report released Tuesday.

As sales declined, home prices climbed in the region.

Southern California’s median home price jumped 20 percent in December from a year ago, according to La Jolla-based DataQuick, driven by strong investment activity, a record number of cash buyers and a continued shift to mid- and high-end sales.

But industry professionals say the lower rate of sales in the Inland Empire was not so surprising.

“It does not surprise me that sales are down,” said Michael Carney, who runs the Real Estate Research Council of Southern California and is a professor at Cal Poly Pomona. “There’s clearly a supply constraint. Realtors will tell you they want more inventory. They’re sure they could sell more houses if someone would just put them on the market.”

This report, he says, shows the increase in San Bernardino and Riverside counties’ home values is greater than the other four counties – Los Angeles, San Diego, Orange and Ventura – and those are the biggest of the six counties.

The Southern California average is heavily influenced by Riverside and San Bernardino counties, Carney said.

In San Bernardino County, the median price increased to $180,000 from $150,000 a year ago. The median made double- digit percentage gains in all six counties.

Riverside County’s median price rose to $231,000 from $194,000, while in Los Angeles County, the median price increased to $323,000 from $270,000 a year earlier.

The median made double-digit percentage gains in all six counties studied by DataQuick.